It seems you have a relatively old PC. You should list what components you have before any suggestions can be made.
Star Wars: Knights of the Old Republic 1 & 2 are examples of old, but good RPG games.
Neverwinter Nights 1 & 2 are also good RPG games which are slightly newer than than the Star Wars games mentioned above.
The Elder Scrolls: Morrowind is also pretty good. The storyline is immersive, but combat is a bit lackluster.
The Mass Effect trilogy is a more recent series of 3rd person RPG games. They have relatively low requirements (playable on any laptop that has an Intel "Sandy Bridge CPU" with the integrated Intel HD 3000 graphic core @ 1366x768 resolution, but it may be more than what your computer / laptop can handle depending on it's hardware. The Mass Effect trilogy is a bit unique because you can import saved games from Mass Effect 1 & 2. The choices you make in prior games can have small and large consequences in Mass Effect 2 and ultimately in Mass Effect 3.